WIEN2k software package

An Augmented Plane Wave Plus Local Orbital

Program for Calculating Crystal Properties

 Peter Blaha

Karlheinz SchwarzGeorg Madsen

Dieter KvasnickaJoachim Luitz

November 2001Vienna, AUSTRIA

Vienna University of TechnologyWIEN97: ~500 usersWIEN2k: ~450 users

General remarks on WIEN2k

WIEN2k consists of many independent F90 programs, which are linked together via C-shell scripts.

Each „case“ runs in his own directory ./case The „master input“ is called case.struct Initialize a calculation: init_lapw Run scf-cycle: run_lapw (runsp_lapw) You can run WIEN2k using any www-browser and the w2web interface, but also at the command line of an xterm.

Input/output/scf files have endings as the corresponding programs:

case.output1…lapw1; case.in2…lapw2; case.scf0…lapw0 Inputs are generated using STRUCTGEN(w2web) and init_lapw

Program execution:

All programs are executed via the „master“ shell-script „x“:

x lapw2 –up –c This generates a „def“ file: lapw2.def

5,'tin.in2c', 'old', 'formatted'

6,'tin.output2up', 'unknown','formatted'

8,'tin.clmvalup', 'unknown','formatted'

10,'./tin.vectorup','unknown','unformatted' and executes: lapw2c lapw2.def All WIEN2k-shell scripts have long and short names:

x_lapw; runsp_lapw, runfsm_lapw x; runsp; runfsm All scripts have a „help“ switch „-h“, which explains flags and options (without actually execution)

x –h x lapw1 -h

w2web: the web-based GUI of WIEN2k

Based on www WIEN2k can be managed

remotely via w2web Important steps:

start w2web on all your hosts login to the desired host (ssh) w2web (at first startup you

will be asked for username/ password, port-number, (master-)hostname. creates ~/.w2web directory)

use your browser and connect to the (master) host:port

opera http://fp98.zserv:10000 create a new session on the

desired host (or select an old one)

w2web GUI (graphical user interface)

Structure generator spacegroup selection

step by step initialization symmetry detection automatic input generation

SCF calculations Magnetism (spin-polarization) Spin-orbit coupling Forces (automatic geometry

optimization) Guided Tasks

Energy band structure DOS Electron density X-ray spectra Optics

Structure generator

Specify: Number of nonequivalent atoms lattice type (P, F, B, H, CXY, CXZ, CYZ) or spacegroup symbol lattice parameters a,b,c (in Ang or bohr) name of atoms (Si) and fractional coordinates (position)

as numbers (0.123); fractions (1/3); simple expressions (x-1/2,…) in fcc (bcc) specify just one atom, not the others in (1/2,1/2,0; …)

„save structure – continue editing – save structure – save+cleanup updates automatically Z, r0, equivalent positions and generates case.inst

After „init_lapw / nn“ you know the distances between the atoms. Go back to structgen and specify RMT:

non-overlapping „as large as possible“ (saves time), but not larger than 3 bohr

RMT for sp-elements 10-20 % smaller than for d (f) elements largest spheres not more than 50 % larger than smallest sphere Exception: H in C-H or O-H bonds: RMT~0.6 bohr (RKMAX~3-4) Do not change RMT in a „series“ of calculations

Program structure of WIEN2k

init_lapw initialization symmetry detection (F, I, C-

centering, inversion) input generation with

recommended defaults quality (and computing time)

depends on k-mesh and R.Kmax (determines #PW)

run_lapw scf-cycle optional with SO and/or LDA+U different convergence criteria

(energy, charge, forces) save_lapw

tic_gga_100k_rk7_vol0 cp case.struct and clmsum

files, mv case.scf file rm case.broyd* files

scf-cycle

run_lapw [options] (for nonmagnetic cases) -ec 0.0001 convergence of total energy (Ry) -cc 0.0001 convergence of charge distance (e-) -fc 1.0 convergence of forces (mRy/bohr) -p parallel calculation (needs .machines file) -so add spin-orbit Spacegroups without inversion use automatically lapw1c, lapw2c

(case.in1c,in2c) If scf-cycle diverges (grep :DIS case.scf): check struture; reduce

mixing in case.inm; rm *.bro* case.scf; x dstart runsp_lapw (for magnetic cases, case.clmup/dn)

-orb use LDA+U (needs case.indm, case.inorb) runfsm_lapw –m Moment (fixed-spin-moment calc.)

runafm_lapw (Antiferromagnetic, use with care)

case.in1

WFFIL (WFPRI, SUPWF) 7.00 10 4 (R-MT*K-MAX; MAX L IN WF, V-NMT 0.30 5 0 global E-param with N other, napw 0 0.30 0.000 CONT 1 Es 0 -3.72 0.005 STOP 1 Es-LO with search 1 -2.07 0.010 CONT 1 Ep with search 1 0.30 0.000 CONT 1 Ep-LO 2 0.30 0.010 CONT 1 0/1…LAPW/APW+lo

',

max),(

lNSLMl

NSmn

l

l lmlllmK

KMAX

K

riKK

VH

YrEuA

ec

n

n

n

n

case.in1 (cont.), case.in2

K-VECTORS FROM UNIT:4 -7.0 1.5 emin/emax window GAMMA 0 0 0 40 1.0 IX, IY, IZ, IDIV, WEIGHT 1 0 0 40 6.0 ... X 40 0 0 40 3.0 END

case.in2: TOT (TOT,FOR,QTL,EFG,FERMI) -9.0 16.0 0.50 0.05 EMIN, NE, ESEPARMIN, ESEPAR0 TETRA 0.000 (GAUSS,ROOT,TEMP,TETRA,ALL eval) 0 0 4 0 4 4 6 0 6 4 0 0 4 0 4 4 6 0 6 4 14. GMAX(for small H set it to 20-24) FILE FILE/NOFILE write recprlist

LM

GMAX

G

iGrGLMLM errYrr )()ˆ()()(

run_lapw -ql 0.05 -in1new 1

Alternative case.in1 file produced by write_in1:

case.scf2: Energy to separate semicore and valencestates: 0.34941 :FER : F E R M I - ENERGY(TETRAH.M.)= 0.79528 Q-s-low E-s-low Q-p-low E-p-low Q-d-low E-d-low :EPL01:1.9813 -2.6852 5.5892 -1.1099 0.0873 0.0910 Q-s-hi E-s-hi Q-p-hi E-p-hi Q-d-hi E-d-hi :EPH01:0.0668 0.5152 0.1752 0.6174 1.0614 0.6181

case.in1: WFFIL (WFPRI, SUPWF) 7.00 10 4 .49528 6 0 0 0.515 0.000 CONT 1 0 -2.685 0.000 CONT 1 1 0.617 0.000 CONT 1 1 -1.110 0.000 CONT 1 2 0.618 0.000 CONT 1 2 0.091 0.000 CONT 1 ...

EF

DOS

E

E-separmin

E-separ0

E-separ

vale

nce

semi-core

Getting help

*_lapw –h „help switch“ of all WIEN2k-scripts help_lapw:

opens usersguide.pdf; Use ^f keyword to search for an item („index“) html-version of the UG: ($WIENROOT/SRC_usersguide/usersguide.html)

http://www.wien2k.at/reg_user FAQ page with answers to common questions Update information: When you think the program has an error, please

check newest version Textbook section: DFT and the family of LAPW methods by S.Cottenier Mailing-list:

subscribe to the list (always use the same email) check the „digest“ (your questions may have been answered before) posting questions: Provide sufficient information, locate your problem

(case.dayfile, *.error, case.scf, case.outputX). „My calculation crashed. Please help.“ This will most likely not be

answered.

Task for electron density plot

A task consists of a series of steps that must be executed to generate a plot

For electron density plot select states by energy

window in case.in2 (e.g. valence e-: Ti-3d,4s, C-2s,2p)

for difference densities make sure you calculate the same states for the free atoms

select plane for plot (do not put an atom at the corner or edges)

generate 3D or contour plot with gnuplot or Xcrysden (Tone.Kokalj@ijs.si)

reset EMIN in case.in2

TiC electron density

NaCl structure (100) plane Valence electrons only plot in 2 dimensions Shows

charge distribution covalent bonding

between the Ti-3d and C-2p electrons

eg/t2g symmetry

Properties with WIEN2k - I

Energy bands classification of irreducible representations ´character-plot´ (emphasize a certain band-character)

Density of states including partial DOS with l and m- character (eg. px , py , pz )

Electron density, potential total-, valence-, difference-, spin-densities, of selected states 1-D, 2D- and 3D-plots (Xcrysden) X-ray structure factors Bader´s atom-in-molecule analysis, critical-points, atomic basins

and charges ( ) spin+orbital magnetic moments (spin-orbit / LDA+U)

Hyperfine parameters hyperfine fields (contact + dipolar + orbital contribution) Isomer shift Electric field gradients

0. n

Properties with WIEN2k - II

Total energy and forces optimization of internal coordinates, (MD, BROYDEN) cell parameter only via Etot (no stress tensor) elastic constants for cubic cells Phonons via supercells

interface to PHONON (K.Parlinski) – bands, DOS, thermodynamics, neutrons

Spectroscopy core levels (with core holes) X-ray emission, absorption, electron-energy-loss (core-

valence/conduction bands including matrix elements and angular dep.)

optical properties (dielectric function, JDOS including momentum matrix elements and Kramers-Kronig)

fermi surface (2D, 3D)

Properties with WIEN2k - III

New developments (in progress) non-linear optics non-collinear magnetism transport properties (Fermi velocities, Seebeck, conductivity,

thermoelectrics, ..) Compton profiles linear response (phonons, E-field) (C.Ambrosch-Draxl) stress tensor (C.Ambrosch-Draxl) exact exchange, GW grid-computing

Cohesive energy

Ecrystal: scalar-relativistic valence (or approx. SO)

Eatom : LSTART: fully-relativistic inconsistent description for heavier elements (2nd row):

supercell with one atom in a ~30 bohr FCC box (identical RMT, RKmax, 1 k-point, spinpolarized)

atomB

atomA

crystalcohesBA EyExEEyx

.

Symmetry:

WIEN „preserves“ symmetry: c/a optimization of „cubic“ TiC:

change c lattice parameter in TiC.struct (tetragonal distortion, #sym.op=0)

init_lapw change c back to cubic x optimize …

„Jahn-Teller“ distortion: when you start with a perfect octahedra, you will never get

any distortion start with slightly distorted positions

c/a

Supercells

(0,0,0) P 8 atoms (0,0,0) (.5,0,0) (.5,.5,0) (.5,.5,.5)

(0,.5,0) (.5,0,.5) (0,0,.5) (0,.5,.5)

B 4 atoms yes yes no no F 2 atoms yes no no

yes

4x4x4 supercells: P (64), B (32), F (16) atoms

2x2x2 = 8 atoms

Supercells

Program „supercell“: start with „small“ struct file specify number of repetitions in x,y,z (only integers, e.g. 2x2x1) specify P, B or F lattice add „vacuum“ for surface slabs (only (001) indexed surfaces)

You must break symmetry!!! replace (impurities, vacancies) or displace (phonons) at least 1

atom

At present „supercell“ works only along unit-cell axes!!!

supercells (1 2 atoms)22 x

Surfaces

2D-slabs with finite number of layers with „vacuum“ in 3rd dimension

bcc (001) 7 layers:

aa

a

( 0 0 6z) (.5 .5 ±3z) with lattice parameters:(.5 .5 5z) ( 0 0 ±2z) a, c=(3a+15-20 au vacuum)( 0 0 4z) shift to (.5 .5 ±z)(.5 .5 3z) ( 0 0 0) z= a/2c( 0 0 2z) inversion(.5 .5 z)( 0 0 0)

bcc (110): a +/-2z

+/-z

z=0

orthorhombic CXY-lattice: a, , ca2

a2

(0 0 0) z=a/ c(0 .5 ±z)(0 0 ±2z)

a2

Atoms in Molecules

Theory to characterize atoms and chemical bonds from the topology of the electron density, by R.F.Bader (http://www.chemistry.mcmaster.ca/faculty/bader/aim/aim_0.html)

Electron density of C2H4

AIM-II

Bonds are characterized by „critical points“, where 0•density maximum: (3,-3); 3 negative curvatures , (nuclear max, N-NM)•bond CP: (3,-1): 2 negative, 1 positive (saddle point)

•positive (and large) Laplacian: ionic bond•negative Laplacian: covalent bond

•bridge CP: (3,1)•cage CP: (3,3) (minimum)

trajectories of constant originating at CPs in C2H4

H

C(3,-1) BCP

AIM-III

“Atoms” are regions within a zero-flux surface 0 n

of C2H4 with zero-flux linesdefining atomic basins

CH4

LiH

AIM-IV

Bader analysis of some inorganic compounds:

(e/A3) (e/A5) Q (e)

Cl2 1.12 -6.1 -

I2 0.48 -0.9 -

TiC 0.51 1.8 1.7

TiN 0.47 3.9 1.7

TiO 0.43 5.8 1.5

KCl 0.08 1.2 0.6

Cl2 more covalent than I2

more ionic, but less charge?

less ionic than TiC ?

x aim [-c] You must have a “good” scf-density (case.clmsum)

no core leakage, LMs up to L=8-10 in case.in2 case.inaim (for integration of atomic basins):

SURF1 atom in center of surface (including MULT)20 0.0 1.570796327 theta, 20 points, from zero to pi/220 0.0 0.785398163 phi, from 0 to pi/4 (depends on symmetry!!) 0.07 1.0 4 step along gradient line, rmin (has reached an atom) 1.65 0.1 initial R for search, step (a.u)3 3 3 nshellIRHO "INTEGRATE" rhoWEIT WEIT (surface weights are available in case.surf) 30 30 radial points outside min(RMIN,RMT)END

case.inaim (for critical points)

CRIT1 atom around you search for critical pointsALL two, three, four, all

(dimers,trimers,....all=2+3)3 3 3 nshellEND

extractaim_lapw case.outputaim: extracts CPs and converts units to file critical_points_ang :PC x, y, z, l1, l2, l3, character, laplacian, rho

Relativistic effects:

Dirac equation in central field (spherical symmetry):

)(1

2

1

482 2222

2

23

42

sldr

dV

rcmrdr

dV

cmcm

pV

m

p

non-rel.SE mass+Darwin spin-orbit

Due to SO spin s and orbital angular momentum l are no longer good quantum numbers. Instead use total angular momentum slj

j=l+s/2 =-s(j+½) occupation

l s=-1s=+

1s=-1

s=+1

s=-1s=+

1

s 0 1/2 -1 2

p 1 1/2 3/2 1 -2 2 4

d 2 3/2 5/2 2 -3 4 6

f 3 5/2 7/2 3 -4 6 8

Thorium

6d3/2

7s

6p3/2

6p1/2

6s

-0.24 Ry-0.32 Ry

-1.55 Ry-2-12 Ry

-3.33 Ry

Scalar relativistic approximation

Drop all terms which depend on , keep Darwin and enhanced mass M and modified large ğ and small ƒ̃ ̀component of

dr

gd

Mcf

c

VmMwith

gdr

gd

dr

dV

cMg

r

ll

MrV

dr

gdr

dr

d

Mr~

2

1~

2

~~

4

1~)1(

2

1)

~(

2

1

2

22222

2

Spin s and l are still good quantum numbers.The four-component wave function ̃ contains ̃ as pure spin state

slmYg

~~~

~~

Spin-orbit in second variation

Use the scalar-relativistic (pure-spin) eigenstates ̃ as basis and add Spin-orbit interaction:

00

01

4

1~~~22

l

dr

dV

rcMHHH SOSO

SO mixes spin-up and dn states.

Scalar-relativistic p-orbital is similar to p3/2 wave function, thus ̃ does not contain p1/2 basis:

Add “Local orbital” with p1/2 radial function

Relativistic semi-core states in fcc Th

additional local orbitals for 6p1/2 orbital in Th Spin-orbit (2nd variational

method)

J.Kuneš, P.Novak, R.Schmid, P.Blaha, K.Schwarz,Phys.Rev.B. 64, 153102 (2001)

Spin-orbit coupling

WIEN2k offers several levels of treating relativity: non-relativistic: select NREL in case.struct (not recommended) standard: fully-relativistic core, scalar-relativistic valence

mass-velocity and Darwin s-shift, no spin-orbit interaction “fully”-relativistic:

adding SO in “second variation” (using previous eigenstates as basis)

adding p-1/2 LOs to increase accuracy (caution!!!)x lapw1 (increase E-max for more

eigenvalues, to have

x lapwso a better basis for lapwso)

x lapw2 –so –c SO ALWAYS needs complex lapw2 version

Non-magnetic systems: SO does NOT reduce symmetry. Initso_lapw just generates

case.inso and case.in2c.

Spin-orbit coupling: magnetic systems

magnetic systems: Define direction of magnetism (coupled to the lattice only by

SO, magneto crystalline anisotropy) Possible reduction of symmetry: magnetic field breaks time-

inversion and spin transforms like a pseudovector (current due to magn.field)

number of symmetry operations reduced Irreducible BZ enlarged (do NOT “add” Inversion!) atoms may become non-equivalent, reduced local symmetry

(more LM) initso_lapw (with symmetso) dedects new symmetry and

creates new files (case.struct, in*, clm*). Symmetry operations are classified into

A (preserves real space AND direction of spin) B (preserves real space, inverts magnetic moment). Together with

time-inversion this is still a valid symmetry operation.

spin-orbit coupling: symmetry

[100]

[010]

[001]

[110]

1 A A A A

mx A B B -

my B A B -

2z B B A B

2z

mx

my

direction of magnetization

case.inso

WFFIL4 1 0 llmax,ipr,kpot -10.0000 1.50000 emin,emax (output energy window) 0. 0. 1. direction of magnetization (lattice vectors) 1 number of atoms for which RLO is added 2 -0.97 0.005 atom number,e-lo,de (case.in1), repeat NX times 0 0 0 0 0 number of atoms for which SO is switched off;

atoms

Problems of LSDA

Standard LDA (GGA) gives good description of structural and electronic properties of most materials (lattice parameters within 1-2%, at least qualitatively correct bandstructure, magnetism,…)

Problems: “localized” (correlated) electrons late 3d transition metal oxides (NiO, cuprates)

metals instead of insulators nonmagnetic instead of anti-ferromagnetic

4f (5f) electrons all f-states pinned at the Fermi energy orbital moments too small

“weakly” correlated metals FeAl is ferromagnetic in theory, but nonmagnetic experimentally 3d-band position, exchange splitting,…

Is LSDA repairable ?

ab initio methods GGA: usually improvement, but often too small. Exact exchange: imbalance between exact X and approximate

C GW: gaps in semiconductors, but groundstate? expensive! Quantum Monte-Carlo: very expensive

not fully ab initio Self-interaction-correction: vanishes for Bloch states Orbital polarization: Hund’s 2nd rule by atomic Slater-

parameter LDA+U: strong Coulomb repulsion via external Hubbard U

parameter DMFT: extension of LDA+U for weakly correlated systems

LDA+U method

Separation of electrons into two subsystems: itinerant electrons (described by LSDA) Localized d (f) electrons:

N…total number of e- nm, …orbital occupancies

Hubbard U describes the coulomb energy cost to place two electrons at the same site:

J is the averaged intraatomic exchange parameter

2,

22 )(21

21

21

mee nJUNJUNE

11

)(2)1()1(nnnn

nEnEnEU

LDA+U Functional

Define a new energy functional:

Double counting term Fdc can be approximated in several ways Fully localized limit (Anisimov etal.): Assumes that the total number of

d (f) electrons N= nm is given properly by LDA (but not the eigenvalues). Their energy is (SIC free Hartree energy):

Around mean field approximation (Czyzyk&Sawatzky):

Orbitals with occupancies nm,m’, larger than ½ (or naverage) become more occupied, others become depopulated.

)()( mdc

meeLDAULDA nFnEFF

)21)((

2)1(2

',,',,

2

mmmm

dc

nJUV

NJNNUE

))((

)(21

21

21

',,,',,

2,

22

mmavermm

averdc

nnJUV

nJUNJUNE

can shift center of bands

leaves center unchanged

rotational invariant LDA+U

In essence, LDA+U shifts occupied states down in energy by U/2 and empty states up.

A generalization leads to the “rotational invariant LDA+U” method, which is independent of coordinate systems, uses the full density matrix nm,m’ and two parameters, Hubbard U and Stoner exchange J.

U and J can be taken from experiment or estimated by constraint LDA calculations. (U … 2-10 eV, J … 1-2 eV)

Cuprates

La2CuO4: nonmagnetic metal instead of AFM insulator

lower Hubbard-band

upper HB

Cuprates: partial Cu-d DOS

Cuprates: Cu-moment vs. U

runsp_lapw -orb

cp $WIENROOT/SRC_templates/case.inorb .cp $WIENROOT/SRC_templates/case.indm .

Specify atoms, orbitals and U, J

Note: Different solutions may be obtainedwhen starting from different density matrices.

WIEN2k- hardware/software

WIEN2k runs on any Unix/Linux platform from PCs, workstations, clusters to supercomputers

Pentium-IV with fast dual memory bus (1-2 Gb memory, 100Mbit net, IDE disks)

10 atom cells on 128Mb PC / 100 atom cells require 1-2 Gb RAM installation support for most platforms

Fortran90 (dynamical allocation, modules) real/complex version (inversion) many individual modules, linked together with C-shell or perl-

scripts

web-based GUI – w2web (perl)

f90 compiler, BLAS-library (ifc+mkl), perl5, ghostscript (+jpg), gnuplot(+png), Tcl/Tk (Xcrysden), pdf-reader, www-browser

Installation of WIEN2k

Register via http://www.wien2k.at Create your $WIENROOT directory (e.g. ./WIEN2k ) Download wien2k_03.tar and examples (executables) Uncompress and expand all files using:

tar –xvf wien2k_03.tar gunzip *.gz chmod +x ./expand_lapw ./expand_lapw

This leads to the following directories: ./SRC (scripts, ug.ps) ./SRC_aim (programs) … SRC_templates (example inputs) … SRC_usersguide_html (HTML-version of UG) example_struct_files (examples) TiC

siteconfig_lapw

**************************************************** * W I E N * * site configuration * **************************************************** S specify a system C specify compiler O specify compiler options, BLAS and LAPACK P configure Parallel execution D Dimension Parameters R Compile/Recompile U Update a package L Perl path (if not in /usr/bin/perl) Q Quit

D: define NMATMAX (adjust to your hardware/paging!): NMATMAX=5000 256Mb (real) or 500Mb (complex) NMATMAX=10000 1Gb (real) 80-150 atoms/unitcellAlways use „optimized“ BLAS library (ifc+mkl; ATLAS-BLAS)

userconfig_lapw

Every user should run userconfig_lapw support for tcsh and bash sets PATH to $WIENROOT, sets variables and aliases

$WIENROOT, $SCRATCH, $EDITOR, $PDFREADER pslapw: ps –ef | grep lapw lsi: ls –als *.in* lso: *.output* lss: *.scf* lsc: *.clm*

w2web: acts as webserver on a userdefined (high) port. define „master“ and „slave“ nodes. (master knows all „projects“) define user/password and port. (http://host.domain.xx:5000) ~/.w2web/hostname/conf/w2web.conf: (configuration file)

deny=*.*.*.* allow=128.130.134.* 128.130.142.10 define execution types: NAME=commands (eg.: batch=batch < %f)

Parallelization

k-point parallel on clusters (slow network): lapw1+lapw2 common NFS filesystem (files must be accessable with the same

path on all machines) rsh/ssh without password (.rhosts; private/public keys)

.machines file: 1:host1 (speed:hostname) 2:host2 granularity:1 (1:10k+10k; 3: 3+3+3+3+3+3+rest load balancing) extrafine (rest in junks of 1 k)

testpara (tests distribution); run_lapw -p

fine-grain parallelization for big cases (>50 atoms) and fast network (shared memory machines)

mpi + scalapack .machines file:

1:host1:4 4 mpi-parallel jobs on host1 lapw0:host1:4 host2:4 8 parallel jobs; atom-loops only!!!

Flow of parallel execution

lapw1para lapw2para

PHONON-I

PHONON by K.Parlinski

(Crakow) runs under MS-

windows uses a „direct“

method to calculate Force-constants with the help of an ab initio program

with these Force-constants phonons at arbitrary k-points can be obtained

Define your spacegroup

Define all atoms

PHONON-II

Define an interaction range (supercell)

create displacement file transfer case.d45 to

Unix Calculate forces for all

required displacements initphonon_lapw

for each displacement a case_XX.struct file is generated in an extra directory

runs nn and lets you define RMT values like:

1.85 1-16• init_lapw: either without symmetry (and then copies this setup to all case_XX) or with symmetry (must run init_lapw for all case_XX) (Do NOT use SGROUP)• run_phonon: run_lapw –fc 0.1 –i 40 for each case_XX

PHONON-III

analyse_phonon_lapw reads the forces of the scf runs generates „Hellman-Feynman“

file case.dat and a „symmetrized HF-file case.dsy (when you have displacements in both directions)

check quality of forces: sum Fx should be small (0) abs(Fx) should be similar for

+/- displacements transfer case.dat (dsy) to

Windows Import HF files to PHONON Calculate phonons